Expandable systems for medical electrical stimulation

ABSTRACT

A medical system for electrical stimulation includes a first column of electrodes, a second column of electrodes, an expandable member disposed between first and second columns, and an expansion mechanism adapted to transmit an externally applied pressure to the expandable member. The pressure expands the expandable member in order to force the first column of electrodes apart from the second column of electrodes. The first and second columns, disposed side-by-side, may be inserted through a percutaneous needle and into a epidural space, alongside a spinal cord; after insertion, the first column may be forced apart from the second column by applying the pressure to the expandable member.

TECHNICAL FIELD

The present invention pertains to systems for medical electricalstimulation and more particularly to stimulation systems that include aexpandable member.

BACKGROUND

Medical electrical stimulation systems typically include one or moreconductors that extend within an elongate insulative lead body and arecoupled to one or more electrodes supported by the body. The one or moreelectrodes are typically coupled to a distal portion of the lead body sothat, when the distal portion is implanted in a patient's body, the oneor more electrodes are positioned to provide electrical stimulationtherapy, for example, pain-relieving spinal stimulation from electrodesimplanted along a spinal cord within an epidural space.

One type of spinal cord stimulation system includes a single column ofelectrodes, which is coupled along a distal portion of a lead body andhas a profile that facilitates percutaneous delivery through a needle toan implant site along the spinal cord within the epidural space. Anothertype of spinal cord stimulation system includes at least two columns ofelectrodes coupled to a distal portion of a lead body; the at least twocolumns are spaced apart from one another so that a profile of thedistal portion is often paddle-like and requires surgical implantation,because the size of the distal portion is too large to fit through aneedle for percutaneous delivery. These paddle-type electrodeassemblies, having more than one column of electrodes, provideflexibility for selection from a variety of stimulation patterns uponimplantation without having to physically reposition the assemblieswithin the epidural space.

Some spinal cord stimulation systems, which include more than one columnof electrodes and which collapse into a smaller profile for percutaneousimplantation, are known in the art. Yet, there is still a need forspinal cord stimulation systems that include more than one column ofelectrodes and are designed to further facilitate operator control overthe systems during an implant procedure thereby increasing an ease ofimplanting the electrode columns at desired locations.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of particular embodiments of thepresent invention and therefore do not limit the scope of the invention.The drawings are not to scale (unless so stated) and are intended foruse in conjunction with the explanations in the following detaileddescription. Embodiments of the present invention will hereinafter bedescribed in conjunction with the appended drawings, wherein likenumerals denote like elements.

FIG. 1A is a plan view of a stimulation system and a percutaneousdelivery needle, according to some embodiments of the present invention.

FIG. 1B is an end view of the system shown in FIG. 1A disposed withinthe needle.

FIGS. 1C-D are an end view and a plan view, respectively, of a distalportion of the system of FIG. 1A in an expanded state or condition.

FIG. 2 is a plan view of an expanded distal portion, according to somealternate embodiments of the present invention.

FIG. 3A is a plan view of a stimulation system, according to someadditional embodiments of the present invention.

FIG. 3B is an end view of the system of FIG. 3A disposed within aneedle, according to some embodiments of the present invention.

FIG. 3C is a plan view of a distal portion of the system of FIG. 3A inan expanded condition.

FIG. 4 is a plan view of an expanded distal portion, according to analternate embodiment of the present invention.

FIG. 5A is a plan view of a stimulation system, according to someadditional embodiments of the present invention.

FIG. 5B is a section view through section line X-X of FIG. 5A, accordingto some embodiments.

FIG. 5C is a plan view of an expanded distal portion of the system shownin FIG. 5A.

FIG. 5D is a schematic end view of the distal portion of FIG. 5Cimplanted along a spinal cord in an epidural space.

FIG. 5E is a schematic end view of an expanded distal portion implantedin the epidural space and having electrodes configured according to somealternate embodiments of the present invention.

FIG. 6A is a plan view of a stimulation system, according to furtheradditional embodiments of the present invention.

FIG. 6B is a section view through section line Y-Y of FIG. 6A, accordingto some embodiments.

FIG. 6C is a plan view of an expansion element, according to someembodiments of the present invention.

FIG. 6D is another plan view of the system of FIG. 6A, wherein a distalportion thereof is expanded, according to some embodiments of thepresent invention.

FIG. 6E is a section view through section line Z-Z of FIG. 6D, accordingto some embodiments.

FIG. 7A is a plan view including a partial cut-away section of astimulation system, according to yet further additional embodiments ofthe present invention.

FIG. 7B is a plan view of the system shown in FIG. 7A wherein a distalportion thereof is expanded, according to some embodiments of thepresent invention.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is notintended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the following description providespractical illustrations for implementing exemplary embodiments of thepresent invention. Examples of constructions, materials, dimensions, andmanufacturing processes are provided for selected elements, and allother elements employ that which is known to those of skill in the fieldof the invention. Those skilled in the art will recognize that many ofthe examples provided have suitable alternatives that can be utilized.

FIG. 1A is a plan view of a stimulation system 1200 and a percutaneousdelivery needle 13, according to some embodiments of the presentinvention. FIG. 1A shows system 1200 configured for insertion intoneedle 13 (according to the dashed line arrow) for percutaneousimplantation, for example, in an epidural space along a spinal cord,according to general implantation techniques which are known to thoseskilled in the art. FIG. 1A illustrates system 1200 including a firstlead body 10 and a second lead body 20, wherein each body 10, 20 extendsfrom a corresponding proximal connector assembly C1, C2 to acorresponding distal column of electrodes 11, 12; electrodes E1 ofcolumn 11 are separated from one another by insulative spacers S1, andeach electrode E1 is coupled by a lead, or elongate conductor (notshown), which extends within body 10, to a corresponding connectorcontact of connector assembly C1; likewise electrodes E2 of column 12are separated from one another by insulative spacers S2, and eachelectrode E2 of column 12 is coupled by a lead (not shown), whichextends within body 20, to a corresponding connector contact ofconnector assembly C2. Those skilled in the art will appreciate thatconnector assemblies C1, C2 (and C3, introduced below) are adapted forcoupling with a pulse generator, which is the electrical stimulationsource for electrodes, and is typically implanted within a subcutaneousspace apart from the stimulation site.

According to an exemplary embodiment, a length of spacers S1, S2 isbetween approximately 0.06 inch and approximately 0.24 inch, and alength of electrodes E1, E2 is approximately 0.12 inch. Column ofelectrodes 11 is shown disposed in proximity to a distal tip D1 of leadbody 10, and column of electrodes 12 is shown disposed in proximity to adistal tip D2 of lead body 20. Although columns of electrodes 11, 12 areshown aligned with one another, so that each electrode E1 is adjacent acorresponding electrode E2, the scope of the invention is not solimited, and, according to other embodiments, one of columns 11, 12 isshifted proximally or distally so that electrodes E1 are not alignedwith electrodes E2 as shown. Furthermore, a number of electrodes E1, E2in each column 11, 12 is not limited to that illustrated herein, and mayrange from two to eight, or even more, for some embodiments.

FIG. 1A further illustrates system 1200 including an elongate tube orsidewall 105, through which a lumen (shown with dashed lines) extends,and an expandable member 100, shown in a collapsed, or unexpanded,state, disposed between columns of electrodes 11, 12. According to theillustrated embodiment, the lumen that extends within sidewall 105provides a passageway for transmission of externally applied pressure toexpandable member 100 in order to expand expandable member 100 to forceapart columns 11, 12, after columns of electrodes 11, 12 have beenpassed through needle 13 and positioned against the spinal cord. Arrow Aindicates a proximal opening of the lumen which provides access for anexpansion mechanism to deliver the externally applied pressure throughthe lumen. It may be appreciated that an initial position of columns ofelectrodes 11, 12, achieved by passing the columns out from the needle,may be adjusted prior to delivering the externally applied pressure toexpandable member 100. According to some preferred embodiments, theexpansion mechanism comprises an inflation medium, which may bedelivered via a syringe-type tool to inflate expandable member 100.Although expansion member 100 is preferably coupled to each lead body10, 20, for example, either all along columns of electrodes 11, 12, orto one or all of spacers S1, S2, or just proximal to columns 11, 12and/or just distal to columns 11, 12, sidewall 105 is, preferably, notcoupled to lead bodies 10, 20, since sidewall 105 is preferably rigidand will not expand when columns 11, 12 are forced apart by expandablemember 100.

FIG. 1A further illustrates needle 13 including a sidewall 130 extendingabout a lumen 132 and longitudinally between a piercing distal tip 137and a proximal hub 135; sidewall 130 includes a slot 134 extending alonga length thereof. FIG. 1B is an end view of system 1200 disposed withinneedle 13, for example, for percutaneous implantation. FIG. 1Billustrates a fit of collapsed system 1200 within a lumen 132 of needle13 wherein sidewall 105 protrudes into slot 134. With reference to FIG.1B, it will be appreciated that expansion element 100, being in acollapsed state, allows both lead bodies 10, 20 to fit side-by-sidewithin needle lumen 132. According to some alternate embodiments,sidewall 105 may be collapsible so that a needle lumen without asidewall slot, such as slot 134, can accommodate both lead bodies 10, 20and sidewall 105. According to some methods of the present invention,once needle 13, via piercing tip 137, has been inserted into an epiduralspace, distal tips D1, D2 of bodies 10, 20 are inserted into needlelumen 132, and bodies 10, 20 are pushed through lumen 132 to advancecolumns of electrodes 11, 12 into the epidural space; after columns 11,12 have been pushed out from needle 13, and positioned at target implantsite along the spinal cord, a pressure is applied to expandable member100 causing member 100 to expand and force columns 11, 12, apart fromone another for example, as illustrated in FIGS. 1C-D. Expandable member100 may be inflated, as previously described, to force columns 11, 12apart, or member 100 may be comprised of a cellular sponge-like materialthat swells when a fluid is injected though the lumen of sidewall 105;additional embodiments of expandable members will be described below.

FIGS. 1C-D are an end view and a plan view, respectively, of the systemof FIG. 1A in an expanded state or condition. FIGS. 1C-D illustrateexpandable member 100 having been expanded to force columns ofelectrodes 11, 12 into a position in which the columns are spaced apartfrom one another by a distance F; columns 11, 12 are preferablyapproximately parallel to one another in the illustrated position.Distance F may range from approximately 1.5 mm to approximately 4 mm,and, according to some embodiments of the present invention, expandablemember 100, or any of the other embodiments of expandable membersdescribed herein, may be expanded to different degrees for multipleseparations, or distances F, between columns of electrodes 11, 12 inorder to provide a flexibility, at the time of implant, in spacingcolumns 11, 12 apart at a distance which is most suitable forstimulation therapy.

FIG. 1D further illustrates expandable member 100 extending alongsideand over a length of columns of electrodes 11, 12, however, expandablemember can vary in location and extent with respect to columns 11, 12 toform alternate embodiments. FIG. 2 is a plan view of an expanded distallead portion, according to some such alternate embodiments. FIG. 2illustrates an expandable member 100′ disposed just proximal to columnsof electrodes 11, 12, and, with dashed lines, an alternate or additionallocation for member 100′. According to the illustrated embodiment,columns 11, 12 have sufficient stiffness to be displaced by therelatively limited extent illustrated for member 100′.

FIG. 3A is a plan view of a stimulation system 1300, according to someadditional embodiments of the present invention. FIG. 3A illustratessystem 1300 including a lead body 30 extending distally from a connectorassembly C3 to a bifurcation from which first and second distal leadbodies 301, 302 extend; first column of electrodes 11 is coupled tofirst distal lead body 301 and second column of electrodes 12 is coupledto second distal lead body 302. Each electrode E1 of column 301 and eachelectrode E2 of column 302 is coupled to a corresponding connectorcontact of connector assembly C3, for example, by a corresponding filarof a multi-conductor coil 39, each filar of coil 39 being a conductivewire, for example MP35N wire, isolated from the others via a coating ofelectrical insulation, for example, comprised of polyimide, PTFE, and/orETFE. FIG. 3A further illustrates a lumen 35 extending within body 30and being surrounded by a sidewall 305 just proximal to expandablemember 100; a proximal opening of lumen 35 is preferably located inproximity to connector assembly C2 for the introduction of an expansionmechanism.

FIG. 3B is an end view of system 1300 assembled within a needle 13′ fora percutaneous implantation; a plan view of needle 13′ would be similarto that of needle 13 as shown in FIG. 1A, with the exception of theabsence of a slot in a sidewall 130′ of needle 13′. As previouslydescribed for system 1200, distal ends D1, D2 may be inserted throughneedle 13′, which has been inserted into the epidural space, and body 30pushed to pass columns of electrodes 11, 12 out from needle 13′ into theepidural space alongside the spinal cord. After columns 11, 12 have beenpositioned at a target stimulation site, expandable member 100 may beexpanded by the expansion mechanism, for example, a pressurizedinflation fluid introduced through lumen 35, in order to force columns11, 12 apart, for example, as illustrated in FIG. 3C. FIG. 3C is a planview showing first and second columns 11, 12 spaced apart from oneanother by expanded member 100 and, preferably, approximately parallelwith one another. As previously described for system 1200, expandablemember 100 may be expanded to different degrees for multiple separationsbetween columns of electrodes 11, 12 in order to provide a flexibility,at the time of implant, in spacing columns 11, 12 apart at a distancethat is most suitable for stimulation therapy.

FIG. 3C further illustrates expandable member 100 extending alongsideand over a length of columns of electrodes 11, 12, but, according toalternate embodiments, expandable member varies in location and extentwith respect to columns 11, 12. FIG. 4 is a plan view of an expandeddistal lead portion, according to some such alternate embodiments.Similar to FIG. 2, FIG. 4 illustrates expandable member 100′ disposedjust proximal to columns of electrodes 11, 12. According to theillustrated embodiment, columns 11, 12 have sufficient stiffness to bedisplaced by the relatively limited extent illustrated for member 100′.Although sidewall 305 through which lumen 35 extends is shown, in bothFIG. 3C and FIG. 4, as extending beyond the bifurcation of body 30,alternate embodiments of the present invention include an expandablemember extending proximally to an opening of lumen 35 in bifurcation,such that lumen 35 need not extend distally beyond bifurcation.

FIG. 5A is a plan view of a stimulation system 1500, according to someadditional embodiments of the present invention; and FIG. 5B is asection view through section line X-X of FIG. 5A, according to someembodiments. FIGS. 5A-B illustrate system 1500 including a first leadbody 510 and a second lead body 520, wherein each body 510, 520 extendsfrom a corresponding proximal connector assembly C1, C2 to thecorresponding distal column of electrodes 11, 12; each electrode E1 ofcolumn 11 is coupled by a corresponding filar of a multi-conductor coil58 to a corresponding connector contact of connector assembly C1;likewise, each electrode E2 of column 12 is coupled by a correspondingfilar of a multi-conductor coil 59 to a corresponding connector contactof connector assembly C2. (Filars of coils 58, 59 may be similar inconstruction to those described above for coil 39.) FIG. 5B shows eachbody 510, 520 including a lumen 56, 57, respectively, and optional innersheaths 508, 509 extending around respective coils 58, 59 and withinrespective lumens 56, 57.

FIGS. 5A-B further illustrate an expandable member 500 disposed betweencolumns of electrodes 11, 12 and formed by walls 515 which are coupledto bodies 510, 520, for example, via adhesive and/or thermal bonding,and an inflation device 570 coupled to a proximal end of body 520; atubular member 578 of inflation device 570 is in fluid communicationwith lumen 57. According to the illustrated embodiment, inflation device570 includes a chamber 507 holding an inflation medium, or fluid, whichacts as an expansion mechanism for transmitting a pressure applied by aplunger 575 of inflation device 570; the inflation fluid, beingtransmitted, through lumen 57 and into expandable member 500, via a port550 of lumen 57, and pressurized by plunger 575, inflates expandablemember 500 by spreading walls 515, for example as illustrated in FIG.5C. After member 500 has been inflated, device 570 may be detached fromlumen 57 and replaced with a plug 52 to seal off the proximal end oflumen 57 in order to maintain inflation pressure within member 500.However, it should be noted that, according to alternate embodiments, itis not necessary to hold the inflation pressure within member 500 inorder to maintain a desired separation between columns 11, 12, after theinitial inflation.

According to preferred embodiments of the present invention, walls 515of expandable member 500 are relatively thin, for example, ranging fromapproximately 0.0002 inch to approximately 0.004 inch, and are formedfrom a relatively compliant material, for example, silicone, low tomedium durometer urethane, or polyolefin copolymer (POC); according toother embodiments, walls 515 are formed from a relatively non-compliantmaterial, for example, polyethylene terephthalate (PET). In someembodiments of the present invention, expandable member 500 mayinitially be formed, according to methods known to those skilled in theart, as a balloon whose outer surface may subsequently be bonded tobodies 510, 520.

FIG. 5C is a plan view of the expanded distal lead portion of system1500; and FIG. 5D is a schematic end view of the expanded distal leadportion implanted along a spinal cord in an epidural space. Withreference to FIGS. 5C-D, it may be appreciated that expanded member 500forces columns of electrodes 11, 12 to be spaced apart from one another,for example, in a configuration mimicking that of a paddle-type surgicallead, and that a flexibility of expanded member 500 facilitatesconformance within the epidural space, such that electrodes E1, E2 ofcolumns 11, 12 make good contact with the dura mater enclosing thespinal cord. FIGS. 5B-D further illustrate with dashed lines additionalexpandable members and corresponding ports (FIG. 5B) extending fromcorresponding lumens 56, 57 for inflation thereof; according to someembodiments of the present invention, these additional members may beadded to enlarge the distal lead portion of system 1500, for a snug fitwithin the epidural space. Alternately, expandable member 500 may expandto a larger size for the snug fit, without compromising electrodecontact with the dura mater, for example as illustrated in FIG. 5E,which is another schematic end view of the expanded distal lead portionimplanted in the epidural space.

Electrodes E1, E2 have heretofore been illustrated as rings extendingabout respective lead bodies, but FIG. 5E illustrates an alternateembodiment: electrodes E1′, E2′, which each have a relatively flatsurface for stimulating contact. Each electrode E1′, E2′ may be formed,for example, as a plate mounted on the respective lead bodies 510, 512,being either coupled directly with the corresponding conductive filar ofrespective coil 58, 59 (FIG. 5B), or coupled to a conductive ring, whichis, in turn coupled to the corresponding conductive filar; an example ofthe latter construction is described for a surgical-type lead inco-pending and commonly assigned patent application Ser. No. 11/413,582,salient portions of which are hereby incorporated by reference.According to other contemplated embodiments, columns of electrodes 11,12 are incorporated into an expandable element, for example, element 100or 500, wherein the electrodes are coupled to a surface of theexpandable element; such electrodes may be rigid or formed from aflexible material, for example, from a foil.

FIG. 6A is a plan view of a stimulation system 1600, according tofurther additional embodiments of the present invention; and FIG. 6B isa section view through section line Y-Y of FIG. 6A, according to someembodiments. FIGS. 6A-B illustrate system 1600 including a lead body 60extending distally from connector assembly C3 to a bifurcation fromwhich a first distal lead body 601, to which column of electrodes 11 iscoupled, and a second distal lead body 602, to which column ofelectrodes 12 is coupled, each extend; each electrode E1 of column 11 iscoupled by a corresponding conductor 691 to a corresponding connectorcontact of connector assembly C3, and each electrode E2 of column 12 iscoupled by a corresponding conductor 692 to a corresponding connectorcontact of connector assembly C3. FIG. 6A further illustrates a singledistal tip D3 terminating distal bodies 601, 602. According to theillustrated embodiment, a lumen 675 extends through lead body 60 from aproximal opening 65, in proximity to connector assembly C3, to a distalopening at the bifurcation, the distal opening providing fluidcommunication between lumen 675 and an expandable area 600, which isenclosed by sidewalls 615.

FIG. 6C is a plan view of an expansion element 670, according to someembodiments of the present invention, which is adapted for insertioninto expandable area 600, via lumen 675. FIG. 6C illustrates expansionelement 670 including a first elongate member 674 extending within asecond elongate member 676, and an expandable member 607. FIG. 6Cfurther illustrates a distal end of second elongate member 676 coupledto a proximal end 617 of expandable member 607, and a distal end offirst elongate member 674 coupled to a distal end 627 of expandablemember 607, so that elongate member 674 forms an expansion mechanism forexpandable member 607. According to the illustrated embodiment, whenfirst elongate member 674 is pulled in a direction corresponding toarrow B, distal end 627 of expandable member 607 is brought closer toproximal end 617 thereby expanding expandable member 607 per arrows C,for example, as illustrated with dashed lines in FIG. 6C, and asillustrated, for some embodiments, in FIG. 6E.

FIG. 6D is another plan view of system 1600, according to someembodiments of the present invention, wherein a distal portion thereofis expanded by insertion and subsequent expansion of expansion element670 within walls 615 of expandable area 600. FIG. 6E is a section viewthrough section line Z-Z of FIG. 6D, according to some embodiments,wherein expandable member 607 is formed by a plurality of flexible slats650, which are coupled together at proximal and distal ends 617, 627,and thus bent outward when first elongate member 674 pulls distal end627 toward proximal end 617. According to the illustrated embodiment,after system 1600, in an unexpanded state (FIG. 6A), has been insertedinto the epidural space alongside the spinal cord, for example, via apercutaneous needle, expansion element 670 may be inserted into proximalopening 65 of lumen 675 and advanced therein until expandable element607 resides in expandable area 600. (Alternately, element 670 may beinserted into area 600 prior to insertion of system 1600 into theepidural space.) When system 1600 is within the epidural space, andexpandable element 607 resides within expandable area 600, firstelongate member 674 of element 607 may be pulled with respect to secondelongate element 676 to expand expandable member 607 thereby expandingexpandable area 600 and forcing first column of electrodes 11 apart fromsecond column of electrodes 12, for example, as illustrated in FIGS.6D-E. According to preferred embodiments, after expansion element 670has expanded expandable area 600, expandable member 607 of element 670may be collapsed, by pushing first elongate member 674 back into theposition shown in FIG. 6C, and element 670 withdrawn from system 1600 toleave the system in the expanded state, as is illustrated in FIG. 6D.

It should be noted that, although body 60 of system 1600 has beendescribed to include lumen 675 for passage of expansion element,alternate embodiments of the present invention need not include such alumen. According to some such alternate embodiments, an entry forpassage of expansion mechanism 670 into expandable area 600 may beformed in body 60 in close proximity to bifurcation and expandable area600, or through one of walls 615 of expandable area 600. According tosome other alternate embodiments, a lumen for passage of expansionelement 670 may be provided by a sidewall external to body 60, whereinthe sidewall extends alongside body 60 to join with expandable area 600being either attached to, or detached from body 60.

FIG. 7A is a plan view including a partial cut-away section of astimulation system 1700, according to yet further additional embodimentsof the present invention. FIG. 7A illustrates system 1700 including alead body 70 extending distally from connector assembly C3 to abifurcation from which distal lead bodies 701, 702 extend tocorresponding distal tips D1, D2; column of electrodes 11 is coupled tolead body 701 and column of electrodes 12 to lead body 702, wherein eachof electrodes E1 is coupled to a corresponding connector contact ofconnector assembly C3 via the corresponding conductor 691, and each ofelectrodes E2 is coupled to a corresponding connector contact ofconnector assembly C3 via the corresponding conductor 692. FIG. 7Afurther illustrates expansion element 670 having been inserted into aproximal port 75 of a lumen 775 of body 70, and advanced within lumen775 so that expandable member 607 has exited lumen 775 at a distal port71. According to the illustrated embodiment, expandable member 607 isdisposed in an area between electrode columns 11, 12, which is notenclosed by expandable walls, for example walls 615 of system 1600, andmay be expanded, as previously described in conjunction with FIGS. 6C-E,to force columns of electrodes 11, 12 apart, for example, as isillustrated in FIG. 7B.

FIG. 7B is a plan view of the system 1700 wherein a distal portionthereof is expanded, according to some embodiments of the presentinvention. FIG. 7B illustrates distal end 627 of expandable member 607having been pulled, via first elongate member 674, per arrow B, toexpand slats 650, thereby spacing apart columns of electrodes 11, 12.According to preferred embodiments, after columns of electrodes 11, 12have been forced into the spaced apart position, expansion element 670is collapsed and withdrawn through lumen 775.

It should be noted that an alternate embodiment of expansion element 670includes a balloon, in place of slats 650, as expandable member 607, andsecond elongate member 676, rather than being disposed about firstelongate member 674, is disposed about an inflation lumen. According tothis embodiment, second elongate member 676 is adapted to couple with aninflation device, for example device 570 shown in FIG. 5A, that willapply a pressure via an inflation medium to expand member 607.

In the foregoing detailed description, the invention has been describedwith reference to specific embodiments. However, it may be appreciatedthat various modifications and changes can be made without departingfrom the scope of the invention as set forth in the appended claims.Furthermore, the embodiments of the invention described herein have beendescribed in the context of spinal cord stimulation, yet those skilledin the art should appreciate that embodiments of the present inventionmay be applied in other contexts, for example, cardiac sensing andstimulation, either endocardial or epicardial.

1. A medical system for electrical stimulation, the system comprising: afirst column of electrodes, and a second column of electrodes extendingalongside the first column of electrodes, each of the first and secondcolumns of electrodes including at least a first electrode separatedfrom a second electrode by an insulative spacer; an expandable memberdisposed between the first and second columns of electrodes; and anexpansion mechanism adapted to transmit externally applied pressure toexpand the expandable member, the expansion of the expandable memberforcing the first column of electrodes and the second column ofelectrodes into a position in which the first and second columns ofelectrodes are spaced apart from one another being approximatelyparallel with one another.
 2. The system of claim 1, wherein: each ofthe first and second columns of electrodes further includes a lengthdefined from a proximal end of the first electrode to a distal end ofthe second electrode; and the expandable member extends along the lengthof the first and second columns.
 3. The system of claim 1, wherein theexpandable member further extends alongside the first and second columnsof electrodes.
 4. The system of claim 1, wherein: the expandable membercomprises an inflatable chamber; and the expansion mechanism comprisesan inflation medium.
 5. The system of claim 1, wherein: the expandablemember includes a first end and a second end and extends between thefirst end and the second end; and the expansion mechanism comprises anelongate member adapted to bring the first end of the expandable membercloser to the second end of the expandable member to expand the member.6. The system of claim 1, further comprising a sidewall surrounding alumen, the lumen extending proximally from the expandable member andproviding a passageway for the transmission of externally appliedpressure.
 7. The system of claim 6, further comprising: a body extendingproximally from one of the first and second columns of electrodes; andwherein the sidewall surrounding the lumen is a part of the body.
 8. Thesystem of claim 6, further comprising: a body extending proximally fromone of the first and second columns of electrodes; and wherein thesidewall surrounding the lumen is separate from the body.
 9. The systemof claim 1, further comprising a body extending proximally from both thefirst and second columns of electrodes, the body including a lumenextending proximally from the expandable member and providing apassageway for the transmission of externally applied pressure.
 10. Thesystem of claim 1, further comprising: another expandable memberextending alongside at least one of the first and second columns ofelectrodes; and wherein the expansion mechanism is further adapted totransmit externally applied pressure to expand the other expandablemember.
 11. The system of claim 1, wherein: the first column ofelectrodes is coupled to a first body, the first body including a distaltip; and the second column of electrodes is coupled to a second body,the second body including a distal tip unattached to the first bodydistal tip, such that, when the first and second columns of electrodesare in the spaced apart position, the first body distal tip is spacedapart from the second body distal tip.
 12. A medical system forelectrical stimulation, the system comprising: a first column ofelectrodes, and a second column of electrodes extending alongside thefirst column of electrodes, each of the first and second columns ofelectrodes including at least a first electrode separated from a secondelectrode by an insulative spacer, and a length defined from a proximalend of the first electrode to a distal end of the second electrode; anexpandable member extending over the length of the first and secondcolumn of electrodes and being disposed between the first and secondcolumns of electrodes; and an expansion mechanism adapted to transmitexternally applied pressure to expand the expandable member, theexpansion of the expandable member forcing the first column ofelectrodes and the second column of electrodes into a position in whichthe first and second columns of electrodes are spaced apart from oneanother being approximately parallel with one another.
 13. The system ofclaim 12, wherein: the expandable member comprises an inflatablechamber; and the expansion mechanism comprises an inflation medium. 14.The system of claim 12, wherein: the expandable member includes a firstend and a second end and extends between the first end and the secondend; and the expansion mechanism comprises an elongate member adapted tobring the first end of the expandable member closer to the second end ofthe expandable member to expand the member.
 15. The system of claim 12,further comprising a sidewall surrounding a lumen, the lumen extendingproximally from the expandable member and providing a passageway for thetransmission of externally applied pressure.
 16. The system of claim 15,further comprising: a body extending proximally from one of the firstand second columns of electrodes; and wherein the sidewall surroundingthe lumen is a part of the body.
 17. The system of claim 15, furthercomprising: a body extending proximally from one of the first and secondcolumns of electrodes; and wherein the sidewall surrounding the lumen isseparate from the body.
 18. The system of claim 12, further comprising abody extending proximally from both the first and second columns ofelectrodes, the body including a lumen extending proximally from theexpandable member and providing a passageway for the transmission ofexternally applied pressure.
 19. The system of claim 12, furthercomprising: another expandable member extending alongside at least oneof the first and second columns of electrodes; and wherein the expansionmechanism is further adapted to transmit externally applied pressure toexpand the other expandable member.
 20. The system of claim 12, wherein:the first column of electrodes is coupled to a first body, the firstbody including a distal tip; and the second column of electrodes iscoupled to a second body, the second body including a distal tipunattached to the first body distal tip, such that, when the first andsecond columns of electrodes are in the spaced apart position, the firstbody distal tip is spaced apart from the second body distal tip.
 21. Amedical system for electrical stimulation, the system comprising: afirst column of electrodes, and a second column of electrodes extendingalongside the first column of electrodes, each of the first and secondcolumns of electrodes including at least a first electrode separatedfrom a second electrode by an insulative spacer; an expandable areaextending between the first and second columns of electrodes, theexpandable area formed by a sidewall attached to each of the first andsecond columns of electrodes; and an expansion element adapted forinsertion within the expandable area in order to force the first columnof electrodes apart from the second column of electrodes, when theexpansion element is expanded within the area.
 22. The system of claim21, wherein the expansion element comprises an inflatable member, aninflation medium, and an inflation device coupled thereto.
 23. Thesystem of claim 21, wherein the expansion element comprises anexpandable member and an elongate member adapted to bring a first end ofthe expandable member closer to a second end of the expandable member toexpand the expansion element.
 24. The system of claim 21, furthercomprising another sidewall surrounding a lumen, the lumen extendingproximally from the expandable area and providing a passageway for theexpansion element.
 25. The system of claim 24, further comprising: abody extending proximally from one of the first and second columns ofelectrodes; and wherein the sidewall surrounding the lumen is a part ofthe body.
 26. The system of claim 24, further comprising: a bodyextending proximally from one of the first and second columns ofelectrodes; and wherein the sidewall surrounding the lumen is separatefrom the body.
 27. The system of claim 21, further comprising a bodyextending proximally from both the first and second columns ofelectrodes, the body including a lumen extending proximally from theexpandable area and providing a passageway for the expansion element.28. The system of claim 21, wherein: the first column of electrodes iscoupled to a first body, the first body including a distal tip; and thesecond column of electrodes is coupled to a second body, the second bodyincluding a distal tip unattached to the first body distal tip, suchthat, when the first column of electrodes is forced apart from thesecond column of electrodes, the first body distal tip is also forcedapart from the second body distal tip.
 29. A method for implantingspinal cord stimulation electrodes, the method comprising: inserting afirst column of electrodes and a second column of electrodes through apercutaneous needle and into an epidural space alongside a spinal cord,the first and second columns being disposed side-by-side duringinsertion; and applying pressure to an expandable member, the expandablemember being disposed between the first and second columns ofelectrodes, and the applied pressure causing the expandable member toexpand, thereby forcing the first column of electrodes and the secondcolumn of electrodes into a position in which the first and secondcolumns of electrodes are spaced apart from one another andapproximately parallel with one another.
 30. The method of claim 29,wherein applying pressure comprises filling the expandable member withan inflation medium.
 31. The method of claim 29, wherein applyingpressure comprises forcing a first end of the expandable member closerto a second end of the expandable member.
 32. The method of claim 29,further comprising applying another pressure to the expandable membercausing the expandable member to expand further, thereby forcing thefirst column of electrodes and the second column of electrodes intoanother position in which the first and second columns of electrodes arespaced further apart from one another.
 33. A medical system forelectrical stimulation, the system comprising: a first body including adistal tip; a second body including a distal tip, the second body distaltip being unattached to the first body distal tip; a first column ofelectrodes coupled to the first body in proximity to the first bodydistal tip, and a second column of electrodes coupled to the second bodyin proximity to the second body distal tip, the second column ofelectrodes extending alongside the first column of electrodes, and eachof the first and second columns of electrodes including at least a firstelectrode separated from a second electrode by an insulative spacer; anexpandable member disposed between the first and second columns ofelectrodes; and an expansion mechanism adapted to transmit externallyapplied pressure to expand the expandable member, the expansion of theexpandable member forcing the first column of electrodes and the firstbody distal tip apart from the second column of electrodes and thesecond body distal tip.
 34. The system of claim 33, wherein: each of thefirst and second columns of electrodes further includes a length definedfrom a proximal end of the first electrode to a distal end of the secondelectrode; and the expandable member extends along the length of thefirst and second columns.
 35. The system of claim 33, wherein theexpandable member further extends alongside the first and second columnsof electrodes.
 36. The system of claim 33, wherein: the expandablemember comprises an inflatable chamber; and the expansion mechanismcomprises an inflation medium.
 37. The system of claim 33, wherein: theexpandable member extends between a first end thereof and a second endthereof; and the expansion mechanism comprises an elongate memberadapted to bring the first end of the expandable member closer to thesecond end of the expandable member to expand the member.
 38. The systemof claim 33, further comprising a sidewall surrounding a lumen, thelumen extending proximally from the expandable member and providing apassageway for the transmission of externally applied pressure.
 39. Thesystem of claim 33, wherein each of the first and second bodies includesa proximal end; and further comprising another body coupled to each ofthe first and second body proximal ends and extending proximallytherefrom.
 40. The system of claim 39, wherein the other body includes alumen extending proximally from the expandable member and providing apassageway for the transmission of externally applied pressure.
 41. Thesystem of claim 33, further comprising: a first connector assembly and asecond connector assembly; and wherein the first body extends proximallyfrom the first column of electrodes to the first connector assembly; andthe second body extends proximally from the second column of electrodesto the second connector assembly.
 42. The system of claim 41, whereinone of the first and second bodies includes a lumen extending proximallyfrom the expandable member and providing a passageway for thetransmission of externally applied pressure.
 43. The system of claim 41,further comprising a sidewall surrounding a lumen, the sidewall beingseparate from the first and second bodies, and the lumen extendingproximally from the expandable member and providing a passageway for thetransmission of externally applied pressure.
 44. The system of claim 33,further comprising: another expandable member extending alongside atleast one of the first and second columns of electrodes; and wherein theexpansion mechanism is further adapted to transmit externally appliedpressure to expand the other expandable member.